Generally, a plurality of logical servers operating on physical servers are often configured of virtual machines and so on. Conventionally, there are the following two problems in case of a communication between the logical servers which operating on the physical servers.
(1) First Problem
The first problem is as follows. There is no case that a protocol header is added as a new identifier to the existing traffic in the existing router and switch, in order to know the communication condition between the logical servers. Therefore, it is difficult for a network manager to grasp in real time, the communication condition on which of routes is used for the communication, how is a communication quality, and where a communication fault has occurred, even if the communication is carried out by using a MAC (Media Access Control) address, an IP (Internet Protocol) address, a VLAN (Virtual Local Area Network) ID (identifier), and so on assigned to the logical server.
(2) Second Problem
The second problem is as follows. In case of an operation condition under the multi-tenant environment such as a data center, there is a case that the IP addresses overlap in case of the communication between virtual machines in the multi-tenant environment. In such a case, it is impossible to carry out the communication, unless the re-numbering of the IP address or address conversion through NAT (Network Address Translation) is carried out. However, in order to carry out the re-numbering of the IP address, it is required to stop service so that a large load is imposed. It should be noted that it is supposed that NAT contains NAPT (Network Address Port Translation) such as IP masquerade. Also, because NAT is dependent on application, the NAT could not be used unless confirming that application is coordinated. Therefore, there was a case which a problem had occurred in the communication among the virtual machines under the multi-tenant environment.
Regarding (1), in the condition that a protocol header as a new identifier is not added to the existing traffic, the router and switch for relay have not a function of grasping a communication flow condition between the virtual machines. Therefore, it is difficult to grasp a communication path, a communication performance, and a communication fault situation in real time.
Regarding (1), there is a VN-Tag technique of Cisco (registered trademark) which can solve the above problems by adding a protocol header as a new identifier to the existing traffic (Non-Patent Literatures 1 and 2). The function of grasping the communication condition is realized in the VN-Tag technique by introducing a special router and switch which can insert the new header into the existing packet is proposed. However, because the new header cannot be grasped by the existing router or switch which cannot grasp the VN-Tag, the communication flow condition between the virtual machines cannot be grasped in the general environment which coexists with the existing network.
Therefore, it is required to allow a network manager to grasp the communication flow condition between the virtual machines in real time while keeping backward compatibility in the existing Internet network.
Regarding (2), in the multi-tenant environment which provides a server, a storage and network environment for a plurality of enterprises by the data center and so on, there is a case that addresses assigned to the virtual machines overlap. In each company, the address assignment in the intranet is typically implementing by using a space of private IP addresses.
It should be noted that the private IP address is an IP address used in the network not connected directly with the Internet (e.g. the in-house network) such as a perfectly closed network which is not connected with an external network (the Internet), and a network connected indirectly with the external network (the Internet) through a router and so on. The private IP address is also referred to as a private address.
Even if the addresses are uniquely assigned in the in-house system, there is a case that the addresses overlap between the companies. Therefore, when the IP addresses assigned to virtual machines on a server outsourced to the data center overlap, the inter-virtual-machine communication between companies (multi-tenants) cannot be conventionally carried out unless the address re-numbering and NAT are carried out. However, there is a problem on operation in case of either of the address re-renumbering or the NAT.
Therefore, in the multi-tenant network of the data center, it is required that the virtual machine communication between multi-tenants can be carried out even under the environment that the IP addresses of the virtual machines overlap, and a network manager can grasp the communication flow condition in real time.
As the related techniques, JP 2008-278478A (Patent Literature 1) discloses a computing system and a communication control method. In this related technique, data showing a pair of a virtual machine and a physical machine on which the virtual machine operates is recorded in a memory shared by the virtual machine and a virtual machine environmental control function. Also, it is determined whether or not a counter-end virtual machine exists on the same physical machine as the virtual machine, based on the above-mentioned recorded data. Also, a multiplicity is changed by the determination. Moreover, when the virtual machine migrates to another physical machine, the above-mentioned recorded data is rewritten.
JP 2007-158870A (Patent Literature 2) discloses a virtual computer system and a network communication method. In this related technique, switching is carried out between a VLAN communication according to a VLAN ID set to a virtual network interface card (NIC) and a VLAN communication according to a VLAN ID set by an OS on the virtual machine which uses the virtual network interface card, based on whether or not to the VLAN ID is set to the virtual network interface card.
It should be noted that in this related technique, VLAN is realized by using a tag VLAN which is standardized in IEEE 802.1Q. In a communication packet prescribed in IEEE 802.1Q, a VLAN tag field is added to a communication packet which does not contain the VLAN tag (VLAN Tag). The VLAN tag field is composed of a tag type and tag control data, and 12 bits of the tag control data are assigned for the VLAN ID.